1 files changed, 53 insertions, 1 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index 50ca17d3cb45..d581e45c0a9f 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -798,6 +798,10 @@ static struct mount *clone_mnt(struct mount *old, struct dentry *root,
         }
 
         mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~MNT_WRITE_HOLD;
+        /* Don't allow unprivileged users to change mount flags */
+        if ((flag & CL_UNPRIVILEGED) && (mnt->mnt.mnt_flags & MNT_READONLY))
+                mnt->mnt.mnt_flags |= MNT_LOCK_READONLY;
+
         atomic_inc(&sb->s_active);
         mnt->mnt.mnt_sb = sb;
         mnt->mnt.mnt_root = dget(root);
@@ -1713,6 +1717,9 @@ static int change_mount_flags(struct vfsmount *mnt, int ms_flags)
         if (readonly_request == __mnt_is_readonly(mnt))
                 return 0;
 
+        if (mnt->mnt_flags & MNT_LOCK_READONLY)
+                return -EPERM;
+
         if (readonly_request)
                 error = mnt_make_readonly(real_mount(mnt));
         else
@@ -2339,7 +2346,7 @@ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
         /* First pass: copy the tree topology */
         copy_flags = CL_COPY_ALL | CL_EXPIRE;
         if (user_ns != mnt_ns->user_ns)
-                copy_flags |= CL_SHARED_TO_SLAVE;
+                copy_flags |= CL_SHARED_TO_SLAVE | CL_UNPRIVILEGED;
         new = copy_tree(old, old->mnt.mnt_root, copy_flags);
         if (IS_ERR(new)) {
                 up_write(&namespace_sem);
@@ -2732,6 +2739,51 @@ bool our_mnt(struct vfsmount *mnt)
         return check_mnt(real_mount(mnt));
 }
 
+bool current_chrooted(void)
+{
+        /* Does the current process have a non-standard root */
+        struct path ns_root;
+        struct path fs_root;
+        bool chrooted;
+
+        /* Find the namespace root */
+        ns_root.mnt = &current->nsproxy->mnt_ns->root->mnt;
+        ns_root.dentry = ns_root.mnt->mnt_root;
+        path_get(&ns_root);
+        while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root))
+                ;
+
+        get_fs_root(current->fs, &fs_root);
+
+        chrooted = !path_equal(&fs_root, &ns_root);
+
+        path_put(&fs_root);
+        path_put(&ns_root);
+
+        return chrooted;
+}
+
+void update_mnt_policy(struct user_namespace *userns)
+{
+        struct mnt_namespace *ns = current->nsproxy->mnt_ns;
+        struct mount *mnt;
+
+        down_read(&namespace_sem);
+        list_for_each_entry(mnt, &ns->list, mnt_list) {
+                switch (mnt->mnt.mnt_sb->s_magic) {
+                case SYSFS_MAGIC:
+                        userns->may_mount_sysfs = true;
+                        break;
+                case PROC_SUPER_MAGIC:
+                        userns->may_mount_proc = true;
+                        break;
+                }
+                if (userns->may_mount_sysfs && userns->may_mount_proc)
+                        break;
+        }
+        up_read(&namespace_sem);
+}
+
 static void *mntns_get(struct task_struct *task)
 {
         struct mnt_namespace *ns = NULL;